I'm using GStreamer to process videos in my project. The input videos can have various formats (both resolutions and aspect-ratio). It can be for example 400x300, 1080p, 4K, 2000x1000, etc.
I would like to downscale videos automatically which are larger than 1080p. So if video is in 4K it should be downscaled to 1080p but if it is in 400x300 format it should be kept in original format.
I've found videoscale pipeline plugin but it does not work as I would like. It is changing scale up and down without any distinctions. Also it is not changing sizes proportionally when only width or height is provided.
Do you know any straightforward way in GStreamer to downscale resolutions automatically to desired size?
GStreamer's caps allow ranges. So I believe you are looking for something like this:
video/x-raw,width=[1,1920],height=[1,1080],pixel-aspect-ratio=1/1
This will keep the same aspect ratio but scales down in case it is required to fit into 1920x1080.
E.g.
gst-launch-1.0 videotestsrc ! video/x-raw,width=4000,height=2000 ! videoscale ! video/x-raw,width=[1,1920],height=[1,1080],pixel-aspect-ratio=1/1 ! autovideosink
Will be scaled down to 1920x960.
And:
gst-launch-1.0 videotestsrc ! video/x-raw,width=400,height=200 ! videoscale ! video/x-raw,width=[1,1920],height=[1,1080],pixel-aspect-ratio=1/1 ! autovideosink
Will stay at 400x200.
Related
I'm trying to create screenshot (i.e. grab one frame) from RTSP camera stream using gstreamer pipeline.
The pipeline used looks like this:
gst-launch-1.0 rtspsrc location=$CAM_URL is_live=true ! decodebin ! videoconvert ! jpegenc snapshot=true ! filesink location=/tmp/frame.jpg
Problem is that the result image is always gray, with random artifacts. It looks like it's grabbing the very first frame, and it doesn't wait for the key frame.
Is there any way how can I modify the pipeline to actually grab first valid frame of video? Or just wait long enough to be sure that there was at least one key frame already?
I'm unsure why, but after some trial and error it is now working with decodebin3 instead of decodebin. Documentation is still bit discouraging though, stating decodebin3 is still experimental API and a technology preview. Its behaviour and exposed API is subject to change.
Full pipeline looks like this:
gst-launch-1.0 rtspsrc location=$CAM_URL is_live=true ! decodebin3 ! videoconvert ! jpegenc snapshot=true ! filesink location=/tmp/frame.jpg
I am trying to get a camera that uses Gstreamer to capture images in a specific interval of time, while searching in the web I found the following line:
gst-launch-1.0 -v videotestsrc is-live=true ! clockoverlay font-desc="Sans, 48" ! videoconvert ! videorate ! video/x-raw,framerate=1/3 ! jpegenc ! multifilesink location=file-%02d.jpg
I believe it would work great, but unfortunately, I don't know how to get it to work with my specific camera, meaning I don't know how to identify my video source in RPi4 and if that is the only thing I have to change to get it to work. I would appreciate either help with the video source, or any other method to get those images.
I have problem with making pipeline in GStreamer.
My pipeline looks like this:
gst-launch-1.0 videotestsrc is-live=true ! videorate ! video/x-raw,framerate=200/1 ! videorate max-rate=50 ! videoconvert ! x264enc bitrate=500000 byte-stream=true ! h264parse ! rtph264pay mtu=1400 ! udpsink host=127.0.0.1 port=5000 sync=false async=true
At this point, I am optimalizing pipeline for application. So instead of videotestsrc in pipeline, there will be appsrc, which gets frames from application, which returns frames. Everytime appsrc asks for frame, application would return one. Camera have about 50 FPS.
I'll help explanation with a picture:
Gray line means time. Let's say camera send frame every 20ms (50 FPS) (red dots) and appsrc asks every 20ms, but asks allways 1ms before camera produces new frame (blue dots). This will generate delay of 19 ms, which I am trying to get low as possible.
My idea is to use videorate ! video/x-raw,framerate=200/1, to let source ask for new frame every 5 ms, which implies the blue dot will be 4 times faster, than camera getting new frames, which mean 4 frames will be equal. After getting those "newest" frames, I want to (without encoding) to limit framerate back to 50 FPS using videorate max-rate=50.
Problem is, my pipeline doesn't work in application; not even as terminal command gst-launch-1.0.
How can I control framerate twice in one pipeline? Is there any other solution?
Use set_property to set/modify properties of your element. The element handle can be obtained using [gst_element_factory_make][1].
rate = gst_element_factory_make("videorate","vrate")
g_object_set("rate","property-name","property-value")
You can set/modify the values based on your requirements when the pipeline is playing.
When I rotate a test pattern 90 degrees:
gst-launch-1.0 -v videotestsrc ! video/x-raw,width=1280,height=720 ! videoflip method=clockwise ! videoconvert ! ximagesink
I have two problems:
The output window is distorted unless I maximize it
The output video window, when maximized, falls outside of my 1920*1080 monitor, so that I only see the upper half of the testsrc pattern
It could be due to ximagesink? If I remember correctly there is some additional application logic required to match window dimensions and buffer dimensions. Usually xvimagesink or glimagesink yield in better results.
I'm launching a gst-launch-1.0 that captures camera images with nvgstcamera. The images are encoded to VP9 video. The video is tee'd to a filesink that saves the video in a webm container and to a VP9 decoder that pipes the images into an appsink.
Later, I want to extract frames from the saved video and run them through the application again. It is important that the frames are absolutely identical to the ones that were piped into the appsink during video capture.
Unfortunately, the decoded frames look slightly different, depending on how you extract them.
A minimal working example:
Recording:
$ gst-launch-1.0 nvcamerasrc ! "video/x-raw(memory:NVMM), format=NV12" ! omxvp9enc ! tee name=splitter \
splitter. ! queue ! webmmux ! filesink location="record.webm" \
splitter. ! queue ! omxvp9dec ! nvvidconv ! "video/x-raw,format=RGBA" ! pngenc ! multifilesink location="direct_%d.png"
Replaying with nvvidconv element:
$ gst-launch-1.0 filesrc location=record.webm ! matroskademux ! omxvp9dec \
! nvvidconv ! pngenc ! multifilesink location="extracted_nvvidconv_%d.png"
Replaying with videoconvert element:
$ gst-launch-1.0 filesrc location=record.webm ! matroskademux ! omxvp9dec \
! videoconvert ! pngenc ! multifilesink location="extracted_videoconvert_%d.png"
Testing image differences:
$ compare -metric rmse direct_25.png extracted_nvvidconv_25.png null
0
$ compare -metric rmse direct_25.png extracted_videoconvert_25.png null
688.634 (0.0105079)
nvvidconv:
videoconvert:
My guess is that this has to do with the I420 to RGB conversion. So videoconvert seems to use a different color conversion than nvvidconv.
Launching the pipeline with gst-launch -v shows that the element capabilities are basically the same for both replay pipelines, the only difference is that videoconvert uses RGB by default, while nvvidconv uses RGBA. Adding the caps string "video/x-raw,format=RGBA" behind videoconvert makes however no difference in color conversion.
Note that this is on an Nvidia Jetson TX2 and I would like to use hardware accelerated gstreamer plugins during recording (omxvp9enc, nvvidconv), but not during replay on another machine.
How can I extract images from the video that are identical to the images running through the pipeline during recording, but without the use of Nvidia's Jetson-specific plugins?
Check for colorimetry information - https://developer.gnome.org/gst-plugins-libs/stable/gst-plugins-base-libs-gstvideo.html#GstVideoColorimetry
Videoconvert for example take these into account when converting images. Depending on the caps found at input and output.
You probably have to check what the Tegra is doing here. Most likely there is a difference if the signal is interpreted as full range or tv range. Or the matrices differ from 601 and 709.
Depending on precision there may still be some loss during the conversion. For metrics at video codecs it may make sense to stay at YUV color space and use only RGB for display if you must.